Diddy1
join:2003-07-19
Sidney, NE
| reply to LLigetfa
Re: Flat Panel vs. Grid
Ok, I think I understand what your getting at. So what your saying is that to either side of the sector, the polarity is being tilted as well.
However, the client we did the test with, is visually in line with the center of the sector. The sector has little down tilt and I've tried in the past to tilt a little more with bad results so we put it back where it was. The tilt, if I go by the gauge printed on the bracket itself, is 1*.
Aaron |
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LLigetfa
join:2006-05-15
Fort Frances, ON
| reply to Diddy1
A dish is very much affected by slight polarity skews. If ever you worked with satellite dishes, you would have come across this. The dish normally has only a single element up in the feedhorn and the signal is literally focused on it.
Panel antennas on the other hand are designed with multiple elements arrayed in such a way as to interact with one another. They are generally also designed to accept signals with skewed polarity as one may expect from multipath.
Downtilt on a sectoral is not uniform along its full beam width. Take as an example an old 33 1/3 LP record player with stacking spindle and put one record up on the stacking part. Now, tilt the record so that the edge touches the platter and you will notice that 90 degrees to either side, there is no down tilt. There is however, polarity skew. Now I realize that this is quite an exaggeration and that in reality, the downtilt on a sectoral would normally be less than 5 degrees, but if one is sloppy in not plumbing the masts on both ends, the errors can compound. The mast should always be plumb and adjustments made to the mount. |
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Diddy1
join:2003-07-19
Sidney, NE | reply to robbin
But, we should always start with a plumb mount, would you agree?
Aaron |
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robbin
Premium,MVM
join:2000-09-21
Leander, TX | reply to Diddy1
I always use a small level to insure that the mount is plumb and level. Then if I want it out of plumb I make the necessary adjustments. |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to LLigetfa
said by LLigetfa  : My guess is the panel is more polarity agnostic while the grid needs to be more precise. I heard that a few degrees off on rotation can really drop off on a grid. When a sector is down-tilted, the further out from centre you go, the greater the polarity rotational skew. Can you elaborate on these to thoughts? I'm thinking when I mount a mast or DSS arm for client antenna, I may be off slightly on polarity. I just eye-balled it. Does anyone actually take steps to ensure plumbness?
Aarom
Aaron |
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
 ·CenturyLink
| reply to Diddy1
said by Diddy1 :But this is a moot point in my situation, the panel DID out perform the grid. But, I respect your objection and thank you for reading and commenting on my post. Oh, I wasn't objecting...just simply pointing out a fact-of-life in the radio world.
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A is A |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to LLigetfa
said by LLigetfa :Also, the panel can make more of multipath signals than can a grid. I also like to add that I learned this little fact here 
The test we did vs. the amount of adjustment was less than a degree. We really did a very thorough test but are results may be skewed due to the fact tha we just used a stock radios own display of RSSI and strength.
Aaron |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to John Galt
said by John Galt :said by superdog :They pick up more of the multipath because of the antenna pattern. Bear in mind that they will also pick up more interference (if any is present in your area) for the same reason. But this is a moot point in my situation, the panel DID out perform the grid. But, I respect your objection and thankyou for reading and commenting on my post.
Aaron |
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Diddy1
join:2003-07-19
Sidney, NE
1 edit | reply to LLigetfa
Your right, I didnt' include RSSI levels, but I will say that they were all low and no properly corresponding to RX/TX levels. Didn't make sens but again, I was reading of the CPE itself and it's own interpretations.
Aaron
Edit: this is in V-pol |
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
·CenturyLink
| reply to superdog
said by superdog :They pick up more of the multipath because of the antenna pattern. Bear in mind that they will also pick up more interference (if any is present in your area) for the same reason.
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A is A |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| reply to LLigetfa
said by LLigetfa :Also, the panel can make more of multipath signals than can a grid. Agreed. Whenever I am installing a customer that has limited LOS, I will always use a panel over a grid. They pick up more of the multipath because of the antenna pattern. See the pictures. The picture on the left is a grid, and the right side is the panel.
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»www.wavecrazy.net Join WISPA today! »www.wispa.org/ |
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LLigetfa
join:2006-05-15
Fort Frances, ON
1 edit | reply to Diddy1
You didn't mention polarity. My guess is the panel is more polarity agnostic while the grid needs to be more precise. I heard that a few degrees off on rotation can really drop off on a grid.
When a sector is down-tilted, the further out from centre you go, the greater the polarity rotational skew.
Also, the panel can make more of multipath signals than can a grid. Keep also in mind that the Rx levels reported are just raw signal strength not reflective of signal quality, so multipath signal that does not help the link will still be seen in the Rx strength.
I think a better head-to-head shootout would be to compare grid to grid and panel to panel between two towers where they are straight shots with little multi-path. |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to milbrath
I considered this, but we spent some extra time at our most distant client today just toying with it. I informed her prior that we'd like to try some things and she was just as curious as we were if it would work etc. We had the 15dbi grid and the 12dbi panel and tweaked each ones settings ever so meticulously and the panel just blew the grid away on both RX and TX. I forgot to mention that with the panel, we set the power to be right at 36db and did not change this once we put the higher gain grid up and the panel still produced a stronger RX at the AP.
Aaron |
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milbrath
join:2006-03-27
Dresden, TN | reply to Diddy1
My guess is wider beamwidth. A panel would be more forgiving than a grid.
BM |
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